Only have to do one edit every 4 months to stay on as editor.

The high turnover probably reflects the more selfish that just join to get their own site added --- however from what I have seen, in addition to that, almost all clean up the category, clear the backlog for the category and add a lot more than just their own site ... after that they just do not continue. In other words, they have still added value to the project. Its those that join, just add their own site and never return are the ones that risk having a "flag raised" and a senior editor might just remove that one site they listed.

CBP